FINAL Flashcards
1
Q
UAS stands for
A
Unmanned Aircraft Systems
2
Q
A UAS consists of
A
1) an aircraft with no pilot on board,
2) a remote pilot station, 3)
a command and control link, and
4) a payload specific to the intended application/operation
3
Q
Other names for UAS
A
drone
Unmanned Aerial Vehicle
Remotely Piloted Aircraft System
Unmanned Aerial System (less common)
Unpiloted Aircraft System (less common)
4
Q
A UAS for civil applications is commonly referred to as a small unmanned aircraft system (sUAS) weighing less than
A
55 pounds
5
Q
the two types of sUAS
A
Fixed-wing
Multirotor
6
Q
Fixed-wing drones have better _____ but are __________
A
battery efficiency, harder to fly
7
Q
Multirotor drones fly by
A
changing the speed of the rotors so that the thrust generated is greater than, equal to or less than the forces of gravity and drag acting on the aircraft
8
Q
The ______ regulates the rules for small UAS operations under 14 CFR 107
A
FAA
9
Q
The maximum allowable altitude for UAS is
A
400 ft
10
Q
Maximum speed for UAS is
A
100 mph
11
Q
Effective 2021, FAA now requires most UAS to be equipped with
A
remote ID
12
Q
How long is UAS certificate of registration good for
A
3 years
13
Q
To operate the controls of a UAS, you need a __________ or ____________
A
remote pilot certificate, be under the direct supervision of a person who holds such a certificate
14
Q
There are two checklists for flying a UAS, one to be done ______ and the other to be done ________
A
before going out to fly, before taking off
15
Q
The first item on the pre-going out to fly checklist is
A
Check the NOAA Aviation Weather Center website for weather conditions
16
Q
A best practice for capturing quality drone data is _________ because __________
A
Fly within 2 hours of local solar noon, Shadows are the shortest and solar radiation intensity is the highest
Note: 12 pm is NOT solar noon
17
Q
Drone images should have _____ % overlap
A
75
18
Q
True or false, ALL aerial images contain geometric distortions
A
True
19
Q
Ways that aerial images can be distorted
A
Shape
Size
Scale
20
Q
Geometric distortions are created due to _______ errors and _______ errors
A
systematic, random
21
Q
Examples of Systematic Distortions are
A
Earth rotation
Earth’s curvature
Atmospheric refraction
Topographic effects
Relief displacement
22
Q
Examples of Random Distortions are
A
Changes in flight altitude
Changes in flight attitude (roll, pitch, yaw)
Changes in velocity
23
Q
Relief displacement
A
Tall objects are displaced away from the center of the air photo
24
Q
Geometric Correction
A
putting pixels in their proper planimetric (x, y) map locations i.e. real-world coordinates referenced to a map projection
25
A geometrically corrected image is often referred to as
an orthophoto
26
Geometric correction of an air photo is also known as
Georeferencing
Georectification
Image-to-map rectification
Geometric transformation
27
Geometric correction requires 4 basic steps:
1) Choose a source
2) Select ground control points (GCPs)
3) Image transformation
4) Accuracy assessment
28
The best source for georeferencing is
Google Earth Pro
29
Examples of Good GCPs
building corners, street corners, large trees, landmarks
30
Examples of Poor GCPs
cars, rocks, shoreline of a beach, center of a field
31
GCPs must be distributed...
evenly across the unreferenced image, starting from edges and working towards the center
32
A minimum of ___ GCPs is required
3
33
More GCPs =
better fit
34
Accuracy Assessment incorporates
the total root mean square error (RMSE)
35
The lower the overall RMSE,
the better the fit is
36
_______ is the most important physical quantity in remote sensing
Radiance
37
Radiance indicates
how much of the energy emitted, reflected, transmitted or received by a surface will be finally received by a remote sensor
38
Remote sensors measure radiance in a different range of wavelengths and then convert radiance signals to
digital numbers (DNs)
39
The DN of each image pixel corresponds to
the average radiance measured electronically over the ground area corresponding to that pixel
40
Theoretically, there is a ________ between radiance measurements and surface reflectance
direct linear relationship
41
reflectance
proportion of radiation reflected from surface objects relative to the total amount of incident energy
42
The ____ - ____ relationship can be used to perform radiometric calibration for air photos
radiance-reflectance
43
Assumptions of Empirical Line Calibration
the darkest object in an image does not reflect or emit any radiation. DN = 0 represents rλ = 0.
the brightest object in an image does not saturate DN (DN < 255)
radiance measurements made by a sensor have a perfect positive linear relationship with surface reflectance
44
The pinhole camera was later replaced by
the
simple lens camera
45
The simple lens camera introduced the adjustable
diaphragm and shutter
46
A diaphragm (a.k.a. aperture stop) controls...
the amount of light reaching the film
47
A shutter is a device that
allows light to pass for a determined period
48
The camera lens is an optical device that
consists of a curved (convex) material that allows light to pass through. The lens bends the light, reassembles the light reflected from the scene, and forms an image on the sensor
49
the process called focus
Moving the lens closer or further from the sensor to channel the light to recreate the image clearly
50
focal length
the distance from the lens at which parallel light rays are focused to a point
51
Shutter controls the duration of exposure (t), also known as
shutter speed
52
Diaphragm controls the diameter (d) of the lens opening during exposure, also known as
aperture
53
Exposure is the amount of...
energy exposed onto the sensor per unit sensor area
54
In photography, aperture is expressed in f-numbers, known as
f-stops
55
A small fstop (e.g., f/1.4) means a
large aperture (wider opening), while a large f-stop (e.g., f/32) means a small aperture (smaller opening)
56
Aperture size has a direct impact on the ______ of a photograph
brightness
57
A smaller f-stop allows _________ into the camera
more light
58
Depth of Field (DoF)
the range of distance of the image that appears acceptably sharp
59
A small f-stop (e.g., f/1.4) makes the foreground objects ______ but the background ______
sharp, blurry
60
A large f-stop (e.g., f/32) aka small aperture brings _______ in focus
all foreground and background objects
61
True/false, both aperture and shutter speed control the amount of light that comes into the camera
True
62
A slower shutter speed lets in ______ light into the camera
more
63
units for aperture
f-stops
64
units for shutter speed
seconds
65
If the shutter speed is slow (e.g., 1/2 s), it can create an effect called
“motion blur”, where moving objects appear blurred along the direction of the motion
66
With longer shutter speed, images appear brighter/darker?
brighter
67
A fast shutter speed ______ the action in the image
freezes
68
ISO
the camera’s sensitivity to light
69
A lower ISO value means ______ sensitivity to light, while a higher ISO means ______ sensitivity
less, more
70
ISO is a camera setting that will
brighten or darken a photo
71
As the ISO number increases, the photo will become
progressively brighter
72
True/false, A photo at ISO 400 is twice brighter than ISO 200
True
73
True/false, You should only raise your ISO when you are unable to brighten the photo via shutter speed or aperture instead
True
74
A photo taken at too high of an ISO will
show a lot of grain
75
when a high ISO is necessary
when you really need to freeze the action in a photo and therefore need a fast shutter speed
76
The aperture value and shutter speed are ________ proportional
inversely
77
True/False, In aerial photography for remote sensing and photogrammetry purposes, the rule of thumb is to slightly underexpose your photos
78
True/False, Overexposure is irreversible
True
79
Filters are
transparent materials that, by absorption or reflection, eliminate or reduce the energy reaching a film in selected portions of the spectrum
80
A low-pass filter
allows lower wavelengths to pass through but blocks higher wavelengths
81
A high-pass filter
absorbs energy below a certain wavelength
82
A band-pass filter
absorbs all other wavelengths except a specific band
83
A band-stop filter
absorbs energy for a specific range of wavelengths but allows other wavelengths to pass through
84
a ______ filter is the most popular colored filter used for black and white photos
yellow
85
A single-lens camera uses ______ bands
wide
86
A multi-lens camera uses ______ bands
narrow
87
Bands on a ______ camera suffer from data contamination from neighboring bands
single-lens camera
88
Photogrammetry is
the science and technology of obtaining reliable spatial measurements and geometric information about surface objects and phenomena
89
True/False, Remote sensing deals with 2D satellite imagery whereas Photogrammetry not only works on 2D imagery, but also more complex 3D models
True
90
True/false, Photogrammetry uses an imaging system rather than collecting data in different wavelengths
True
91
two main branches of Photogrammetry
metric and interpretive
92
Metric Photogrammetry
makes precise measurements and evaluates exact sizes, shapes, positions, distance, angles, areas, volumes, and elevations of surface features
93
Interpretative Photogrammetry
deals in identifying surface objects and judging their significance
94
Aerial photographs are classified as either
vertical or oblique
95
Vertical photo
an aerial photo taken by a camera looking straight down at the ground
96
Oblique photo
an aerial photo taken at an angle
97
Low oblique photo
the horizon is not shown
98
High oblique photo
the horizon is always visible
99
Nadir
the location on the ground that lies directly below the camera
100
Principal Point
the center of a vertical photo – found by the
intersection of lines connecting opposite and diagonal fiducials
101
Nadir is equal to Principal Point in what type of photos
vertical
102
True/False, in oblique photos, it's possible for the nadir to not be shown
True
103
Why when elevation changes, the distance between a-b appears shorter than the distance between c-d (higher elevation) on the photo
Relief Displacement
104
Relief displacement is the
shift in an object’s image position caused by its elevation above a particular datum
105
If an air photo is ________, the displacement of objects in the air photo is in a direction radial from the principal point (or nadir)
vertical
106
All matter with a temperature greater than absolute zero (0 K) emits
thermal energy, or heat
107
Thermal radiation is generated when
heat from the movement of charges in the material is converted to EMR
108
The ______ the particles move, the greater the kinetic energy and the greater the object’s thermal radiation
faster
109
Temperature is the
measure of the average kinetic energy of the particles in a substance
110
True/False, All objects on Earth’s surface emit thermal radiation
True
111
Why we can use thermal sensor to measure an object's surface temperature
There is a direct relationship between temperature and the amount of TIR energy emitted per unit area
112
Why does TIR band imagery have a lower spatial resolution than visible and NIR band imagery?
thermal uses longwave energy, so there is less energy for the sensor to pick up. TIR sensor needs a larger IFOV to ensure enough energy reaches the sensor in order to make reliable measurements
113
what is directly measured by a TIR sensor
M, or the energy that an object emits per unit area
114
why the calculation of LST is much more complicated than the Stefan-Boltzmann Law equation
Need to calculate emissivity
115
The emissivity, ε, of a surface material is
its effectiveness in emitting energy as thermal radiation
116
a blackbody has an emissivity of
1
117
Real objects radiate less thermal radiation than a
blackbody and therefore are called ________
graybodies
118
Emissivity is the ratio of the thermal radiation emitted from a surface material to the radiation from a _________ at the same temperature
blackbody
119
To calculate LST using Ladsat/MODIS/ASTER imagery, you need to know the
Multiplicative Scale Factor and Additive Offset
120
Cause of urban heat island
Building materials absorb long wave radiation during the day
and have lower rates of radiant cooling during the night
121
Urban Heat Island (UHI) Effect
urban areas have higher temperature in comparison to the surrounding rural areas
122
Boundary layer UHI is measured by
weather balloons
123
Surface layer UHI is measured by
rooftop weather station
124
Canopy layer UHI is measured by
weather station at 2-m above the ground
125
Surface UHI is measured with
remotely sensed thermal infrared imagery
126
yellow has no
blue
127
magenta has no
green
128
cyan has no
red
129
Depth of Field (i.e. how much of image is sharp) increases as _________ increases
aperture
130
All the objects in an aerial photo need to be in focus, which means a ______ aperture/______ f-stop should be used
small, large
131
The DLS sensor on a drone _______ so that ________
collects incoming solar radiation, radiance can be converted to reflectance
132
First item on pre-takeoff checklist
Place the UAS on a flat surface and make sure there is no dirt, rock, and debris underneath the UAS
